Iron core for a stationary induction apparatus

ABSTRACT

An iron core for a stationary induction apparatus, such as a transformer or reactor, comprising an alternate laminate of thin amorphous magnetic strips (21a to 21d) and silicon steel sheets (11a to 11d). It is low in electrical loss, and high in workability.

TECHNICAL FIELD

This invention relates to an iron core for a stationary inductionapparatus, such as a transformer or a reactor.

BACKGROUND ART

A laminated core for a stationary induction apparatus, such as atransformer or a reactor, has usually been formed from high-gradesilicon steel sheets which contribute to energy and resource saving.Another material has recently been developed for use in the manufactureof an iron core for a stationary induction apparatus. It is a magneticthin strip which enables a reduction in the electrical loss of the coreto 20 to 80% of the electrical loss of a silicon steel sheet core.

The construction of these iron cores will be described with reference toFIGS. 1 and 2. In FIG. 1, 1a to 1d indicate silicon steel sheets, and inFIG. 2, 2a to 2d designate thin magnetic steel sheets cut from, forexample, a thin amorphous magnetic strip, thin ferronickel strip or thinquenched ferrosilicon strip. 1a and 1b, or 2a and 2b are leg members,and 1c and 1d, or 2c and 2d are yoke members connecting the leg members1a and 1b, or 2a and 2b. The core members 1a to 1d, or 2a to 2d arelaminated with a minimum joint clearance to form a laminated core for astationary induction apparatus.

The laminated core composed of silicon steel sheets as shown in FIG. 1can be efficiently produced, since it is easy to obtain a desired shape.It is, however, very difficult to obtain a laminated core having a smallloss, since it is presently difficult to expect any further improvementin the magnetic properties of silicon steel sheets.

It is easy to obtain a laminated core having a small loss from thinamorphous magnetic steel sheets as shown in FIG. 2, since they ensure asmall electrical loss. A further improvement in their properties can beexpected. A thin magnetic strip is produced by cooling hot moltenmaterial rapidly as it is blown against a roller or the like moving atan ultrahigh speed. This method involves a lot of technical difficulty,and presently enables the production of only a magnetic core materialhaving a thickness of, say, 100 μm and a width of, say, 2 inches. Theproduction of a laminated core from this material involves a great dealof difficulty.

It has hitherto been impossible to obtain an inexpensive laminated corefor a stationary induction apparatus having a small electrical loss ifonly either silicon steel sheets or thin amorphous magnetic strips areemployed. The former material has the disadvantages of failing toachieve a satisfactory reduction in electrical loss, while the latterhas the disadvantage of being very low in workability.

DISCLOSURE OF THE INVENTION

This invention provides an iron core for a stationary inductionapparatus comprising alternately laminated thin amorphous magneticstrips and silicon steel sheets. It is low in electrical loss, and highin workability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a conventional iron core composed ofsilicon steel sheets;

FIG. 2 is a top plan view of a conventional iron core composed ofamorphous magnetic thin strips;

FIG. 3 is a top plan view showing an embodiment of this invention;

FIG. 4 is a sectional view taken along the line IV--IV of FIG. 3; and

FIGS. 5 and 6 are top plan views showing other embodiments of thisinvention.

BEST MODE OF CARRYING OUT THE INVENTION

The invention will be described with reference to the drawings. In FIG.3, 11a to 11d indicate silicon steel sheets laid in a plurality oflayers, and 21a to 21d denote thin amorphous magnetic strips laid in aplurality of layers. They are juxtaposed in a single layer as shown inFIG. 4. 11a, 11b, 21a and 21b are leg members, and 11c, 11d, 21c and 21dare yoke members connecting the leg members 11a, 11b, 21a and 21b. Theyare laminated with a minimum joint clearance.

The thin amorphous magnetic strips 21a to 21d are presently availableonly in a thickness of 100 μm and a width of 2 inches, as stated before.The silicon steel sheets 11a to 11d are available in a thickness of0.28, 0.30 or 0.35 mm. Therefore, the strips 21a to 21d are employed ina plurality m of layers and a plurality n of rows, as shown in FIG. 4,depending on the thickness of the silicon steel sheets 11a to 11d, andthe capacity of the core required. This arrangement enables utilizationof the advantages of the two kinds of materials employed, i.e., thesmall electrical loss of the thin amorphous magnetic strips and the highworkability of the silicon steel sheets.

Although the thin amorphous magnetic strips are disposed inwardly of thesilicon steel sheets according to the embodiment hereinabove described,it is possible to dispose thin amorphous magnetic strips 41a to 41doutwardly of silicon steel sheets 31a to 31d, as shown in FIG. 5. It isalso possible to obtain the same results by disposing thin amorphousmagnetic strips 51a to 51d between silicon steels sheets 61a to 61d, and71a to 71d, as shown in FIG. 6.

Although the invention has been described with reference to iron coresfor single-phase transformers, it is equally applicable to laminatedcores for other stationary induction apparatuses, such as a polyphasetransformer having three or more phases, or a reactor.

I claim:
 1. A magnetic core for a stationary induction apparatuscomprising a plurality of laminates stacked in a first direction, eachsaid laminate comprising an alternate laminate of a thin substantiallyunbent amorphous magnetic strip and a substantially unbent silicon steelsheet, said strip and sheet being disposed to each other in a seconddirection perpendicular to said first direction, wherein each saidlaminate comprises a plurality of silicon steel sheets disposed inwardlyand outwardly of said thin amorphous magnetic strip.
 2. A magnetic corefor a stationary apparatus comprising a plurality of laminates stackedin a first direction, each said laminate comprising an alternatelaminate of a thin substantially unbent amorphous magnetic strip and asubstantially unbent silicon steel sheet, said strip and sheet beingdisposed to each other in a second direction perpendicular to said firstdirection, wherein said silicon steel sheet is disposed inwardly of saidthin amorphous magnetic strip, and closer to the center of said core. 3.A magnetic core comprising a plurality of laminates stacked in a firstdirection, each said laminate comprising an alternate laminate of a thinsubstantially unbent amorphous magnetic strip and a substantially unbentsilicon steel sheet, said silicon steel sheet being disposed inwardly ofsaid amorphous magnetic strip and closer to the center of said core in asecond direction perpendicular to said first direction, wherein eachsaid amorphous magnetic strip comprises a plurality of contiguousamorphous magnetic sheets disposed along said first direction.
 4. Amagnetic core as recited in claim 3, wherein said plurality of amorphousmagnetic sheets are additionally disposed along said second direction.